The present invention relates to pellets, particularly those which disintegrate quickly in aqueous media and which are sufficiently strong to withstand breakage during storage, shipping and handling.
By xe2x80x9cpelletxe2x80x9d, we mean any solid formulation, including but not limited to, tablets, bricks, briquettes, bars, granules, balls, or blocks.
Pellets are well known in the fields of medicine and agriculture and more recently they are being used in detergent applications. Pellets offer certain advantages over granular compositions; they are non-dusting, do not require measuring, take up less space because they are compressed and the ingredients do not separate during transit and storage. However, problems are experienced regarding the dissolution or disintegration of the pellets in use as compared with granular compositions. In the manufacturing process, a balance must be kept between a pellet compacting pressure which is, on the one hand, high enough to ensure that the pellets are well formed and do not crumble during transport and storage, and a pellet compacting pressure which is, on the other hand, low enough to achieve an appropriate solubility/dispersibility profile. It is well known to use an additive to improve pellet dispersability, for example as disclosed in European Patent Application No. 99304428.8, and agents to improve the strength of the pellet so as to avoid the need for high pellet compacting pressure.
Looking specifically at agents which improve the strength of the pellet, GB 983,243 and GB 989,683 describe the use of a water-soluble organic film forming polymer to form on the pellet (briquette) surface a water soluble film which is sufficiently strong to help make detergent tablets resistant to abrasion and accidental breakage, when dry, and sufficiently soluble to help the detergent tablet to disintegrate readily in water. Suitable coating polymers are polyvinyl alcohol and polyvinyl acetate and, to a lesser extent, polyvinylpyrollidone, sodium carboxymethyl cellulose and hydroxypropyl methyl cellulose.
EP-A2-711828 teaches the use of a binder to improve the strength of detergent tablets; preferred binders are selected from polyethylene glycol, polyvinylpyrollidone, and polyacrylates and water soluble acrylate copolymers.
EP-A2-716144 teaches the use of the binders polyethylene glycol, polyvinylpyrollidone, and polyacrylates and water soluble acrylate copolymers in combination with an exterior coating of organic polymer. Suitable coating materials melt between 40 and 80xc2x0 C. and preferably comprise a copolymer of (meth)acrylic acid and maleic acid or anhydride, or neutralised salts thereof.
EP-A1-896052 discloses detergent tablets with improved handling strength and swift dissolution which comprise a non-gelling binder and a coating. Examples of non-gelling binders are taken from the prior art but suitable coating materials are dicarboxylic acids for example selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid and mixtures thereof.
Finally, U.S. Pat. No. 5,883,061 teaches polymeric tablet binders which comprise (meth)acrylic acid, maleic anhydride, alkyl (meth)acrylates, alkylhydroxy (meth)acrylates or styrene monomers in polymerised form. The polymer has a Tg of from +40 to +120xc2x0 C. and a molecular weight of from 10,000 to 120,000.
The aim of the present invention is to provide novel pellets which are strong enough to be shipped, handled and stored without breakage and yet dissolve quickly on contact with water.
Accordingly, the present invention provides a pellet comprising: one or more active ingredients; and either one or both of
(a) one or more binders incorporated within the body of the pellet; and
(b) one or more coating materials on the surface of the pellet;
characterised in that either one or both of the binder and coating materials comprise one or more polymers with a Tg in the range xe2x88x9285 to +35xc2x0 C., and, optionally, wherein the binder and/or coating material comprise a multi-phase polymer and further wherein at least one of the phases of the multi-phase polymer has a Tg in the range xe2x88x9285 to +35xc2x0 C.
It is not necessary for the binder materials and the coating materials to have the same polymer composition.
In a further embodiment of the present invention the pellet may comprise one or more binders with a Tg in the range xe2x88x9285 to +35xc2x0 C. incorporated within the body of the pellet and a coating material on the surface of the pellet which may comprise one or more polymers with a Tg of greater than +30xc2x0 C.
The polymers used in either one or both of the binder and coating materials of the present invention are mostly amorphous. The polymers used in the invention may be soluble or insoluble in water; those which are water insoluble are preferably readily dispersible in water. The binders and coating materials of the present invention comprise polymers with a Tg in the range xe2x88x9285 to +35xc2x0 C. and preferably a Tg in the range from xe2x88x9260 to +10xc2x0 C. These low Tg values are characteristic of xe2x80x9csoftxe2x80x9d polymers, that is, they will form a film or otherwise form an adhesive bond between the detergent granules within the pellet composition under the conditions of tablet manufacture, which, applicants believe, helps to maintain the integrity of the tablet from the point of manufacture, through storage, until used by the customer.
Such binder and/or coating polymers used in the present invention may comprise polymerized residues of one or more of the following monomers: (meth)acrylic acid, (meth)acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate iso-butyl (meth)acrylate or t-butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate iso-bornyl (meth)acrylate, and (meth)acrylate esters of alkylene glycols, polyalkylene glycols and (C1-C30) alkyl substituted polyalkylene glycols including esters of the formula CH2xe2x95x90CR1xe2x80x94COxe2x80x94O(CH2CHR3O)m(CH2CH2CHR3O)nR2 where R1=H or methyl R2=H or C1-C30 alkyl R3=H or C1-C12 alkyl, m=0-40, n=0-40, and m+n is xe2x89xa71, such as hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; C(1-30) substituted acrylamides; vinyl sulfonate, acrylamidopropanesulfonate; dimethylaminopropyl(meth)acrylamide, alkyl vinyl ethers, vinyl chloride, vinylidene chloride, N-vinylpyrollidone, allyl containing monomers; aromatic vinyl compounds such as styrene, substituted styrenes; butadiene; acrylonitrile; monomers containing acetoacetoxy functional groups such as acetoacetoxyethyl methacrylate; vinyl esters of saturated carboxylic acid, e.g., acetate, propionate, neodecanoate; acid or base containing monomers such as, for example, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, N,N-dimethylaminoethyl methacrylate; or combinations thereof. Additionally, crosslinking and grafting monomers such as 1,4-butyleneglycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, diallyl phthalate, divinyl benzene, or combinations thereof may be used. As used herein, by xe2x80x9c(meth)acrylatexe2x80x9d or xe2x80x9c(meth)acrylicxe2x80x9d, we mean either acrylate or methacrylate for xe2x80x9c(meth)acrylatexe2x80x9d and acrylic or methacrylic for xe2x80x9c(meth)acrylicxe2x80x9d.
The polymers used in the present invention may be made using known techniques, for example, solution, emulsion or suspension polymerisation. It is preferred that they are capable of being isolated in solid form, for example by spray drying. To facilitate this, they may comprise a multiphase polymer, that is, they have at least one phase which is relatively hard compared with another phase. Alternatively, a multiphase polymer dissolved or dispersed in water may also be used.
By xe2x80x9cmulti-phasexe2x80x9d polymer we mean polymer particles with at least one inner phase or xe2x80x9ccorexe2x80x9d phase and at least one outer or xe2x80x9cshellxe2x80x9d phase. The phases of the polymers are incompatible. By xe2x80x9cincompatiblexe2x80x9d we mean that the inner and the outer phases are distinguishable using techniques known to those skilled in the art. For example the use of scanning electron microscopy and staining techniques to emphasise differences in the phases is such a technique.
The morphological configuration of the phases of the polymers may be for example, core/shell; core/shell particles with shell phases incompletely encapsulating the core; core/shell with a multiplicity of cores; or interpenetrating network particles.
The first phase may comprise a xe2x80x9csoftxe2x80x9d polymer with a Tg in the range xe2x88x9285 to +35xc2x0 C., preferably a Tg in the range from xe2x88x9260 to +10xc2x0 C. Such inner phase polymers may comprise polymerized residues of one or more of the following monomers: (meth)acrylic acid, (meth)acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate iso-butyl (meth)acrylate or t-butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate iso-bornyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; (meth)acrylate esters, for example, where the ester group is a polyalkyleneoxide or a C(1-30) alkoxylpolyalkyleneoxide; C(1-30) substituted acrylamides; vinyl sulfonate, acrylamidopropanesulfonate; dimethylaminopropyl(meth)acrylamide, alkyl vinyl ethers, vinyl chloride, vinylidene chloride, N-vinylpyrollidone, allyl containing monomers; aromatic vinyl compounds such as styrene, substituted styrenes; butadiene; acrylonitrile; monomers containing acetoacetoxy functional groups such as acetoacetoxyethyl methacrylate; vinyl esters of saturated carboxylic acid, e.g., acetate; propionate, neodecanoate; acid or base containing monomers such as, for example, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, N,N-dimethylaminoethyl methacrylate. Additionally, crosslinking and grafting monomers such as 1,4-butyleneglycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, diallyl phthalate, divinyl benzene, or combinations thereof may be used.
The outer phase (sometimes regarded as a xe2x80x9cshellxe2x80x9d if it encapsulates the inner phase), of the multi-phase polymer may comprise either:
i) a polymer with a relatively high Tg value, for example from +40 to 160xc2x0 C., which makes the outer phase relatively hard. The outer phase may comprise polymerized residues of one or more of the following monomers: (meth)acrylic acid, (meth)acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate iso-butyl (meth)acrylate or t-butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate iso-bornyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; (meth)acrylate esters, for example, where the ester group is a polyalkyleneoxide or a C(1-30) alkoxylpolyalkyleneoxide; C(1-30) alkylsubstituted acrylamides; vinyl sulfonate, acrylamidopropanesulfonate; dimethylaminopropyl(meth)acrylamide, alkyl vinyl ethers, vinyl chloride, vinylidene chloride, N-vinylpyrollidone, allyl containing monomers, sulfonates; aromatic vinyl compounds such as styrene, substituted styrenes; butadiene; acrylonitrile; monomers containing acetoacetoxy functional groups such as acetoacetoxyethyl methacrylate; vinyl esters of saturated carboxylic, e.g. acetate, propionate, neodecanoate; acid or base containing monomers such as, for example, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, N,N-dimethylaminoethyl methacrylate; or
ii) a polymer with a high acid content, for example, a polymer with from 10 to 60% by weight of the polymer of for example, (meth)acrylic acid, preferably from 10 to 50% methacrylic acid and with a Tg in the range from xe2x88x9230 to  greater than 100xc2x0 C. In some cases, this can give a relatively soft outer phase and is not strictly thought of as a xe2x80x9cshellxe2x80x9d. Suitable outer phase polymers of this type are described in EP-A-576128; and U.S. Pat. No. 4,916,171.
iii) polyvinyl alcohol. This alcohol when used as an outer layer is found to stabilise various copolymers with Tg""s in the range from xe2x88x9285 to +35xc2x0 C., for example, vinyl acetate homopolymer; vinyl acetate/ethylene copolymer; vinyl acetate/ethylene/acrylic acid or ester copolymer; vinyl acetate/acrylic acid or ester copolymer such as but not limited to those disclosed in U.S. Pat. Nos. 4,921,898 and 3,827,996.
By xe2x80x9cactive ingredientxe2x80x9d we mean any material which promotes utility of a pellet containing such an active ingredient, in a particular application; for example, the active ingredient may be a material which has activity as a pharmaceutical, an agrochemical, a water treatment agent, a water softening agent, a fabric softening agent, a laundry detergent, a hard surface cleaner, a surface polishing agent, a polish stripping material, a biocide, a stone washing agent or a drain pipe cleaner.
Of particular interest are pellets which contain active ingredients which have activity as a laundry or dishwashing detergent and/or a hard surface cleaner, referred to collectively as detergent-active compounds. The total amount of binder may be from 0.1 to 25% by weight of the pellet, preferably from 0.5 to 15% and particularly preferably from 1 to 5% by weight of the pellet. Such pellets will typically also contain one or more other ingredients which include builders, suitably in an amount of from 5 to 80wt %, preferably from 20 to 80wt %; bleaching agents; processing additives; adjuvants; enzymes; scale inhibitors; emulsifiers; surfactants; soaps; dispersants; zeolites; de-greasing agents; anti-foaming agents; phosphates; phosphonates; optical brighteners; fillers; extenders; soil removers; deflocculating agents; anti-coagulants; anti-drift agents; disintegration agents, including for example, water swellable polymers; water entraining agents, such as, cellulose; plasticizers or coalescing agents, for example, alkylene glycol alkyl ethers, aromatic glycol ethers, alkyl polyglucosides, polysiloxanes, alcohols and alkyl ester acetates; diluents and carriers. Some of these other ingredients will also be applicable for use in non-detergent pellets.
The one or more binders are incorporated within the body of the pellets of the invention by any suitable method. Preferred methods include either
i) forming an aqueous slurry of the pellet materials including the one or more binders, spray drying the slurry to give a granular product and then compacting these granules in a pelletising machine to form pellets; or
ii) grinding together a dry mixture of the pellet materials including the one or more solid binders and then compacting this mixture in a pelletising machine to form pellets;
iii) spraying the one or more binders into the other pellet materials in powder form and then compacting to form pellets; or
iv) dispersing melted binder material into the other pellet materials in solid or powder form and compacting to form pellets.
Typical compacting loads for commercial pellets without the binders of the present invention can be up to 5000 pounds. The binders of the present invention allows the same pellet formulation to be formed using lower compacting loads. The actual compacting load needed will vary depending on the size of the particles, and the composition of the inorganic components of the pellet.
The coating materials are applied to the outer surface of the pellets by any known method, for example, coating with molten material or coating with a solution of the coating material, by dipping, spraying or brush painting. Enhanced pellet strength is achieved if the coating material also comprises a dicarboxylic acid, for example oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid and mixtures thereof. Typically, the amount of coating material applied to a pellet is from 0.1 to 25% by weight of the pellet, preferably from 0.5 to 15% and particularly preferably  less than 5% by weight of the pellet.